Need Help login system Newbie here

I got this code from a site and i followed the instruction to the teeth. But it's not working. I had modified it but still not working.

The Problem is that after the user enters the user name and pass the user does not get redirect to main.php instead it just sits there with a blank page and the url reads http://localhost/re/userlogin.php (where userlogin.php is the page where the user types his user and pass.

This is the orginal code:<?php// we must never forget to start the sessionsession_start();